Field of the Invention
The invention relates in general to a decision feedback equalizer, and more particularly, to a method and device for calculating coefficients of a feed-forward equalizer and a feed-backward equalizer in a decision feedback equalizer.
Description of the Related Art
FIG. 1 shows a functional block of a conventional decision feedback equalizer (DFE). A transmitted signal x(n) passes through a channel 10 and is affected by noise r(n) to become an input signal y(n) of a DFE 100, where n represents a time index. The DFE 100 includes a feed-forward equalizer (FFE) 110, a decider 120, a feed-backward equalizer (FBE) 130, a channel estimator 140, an FFE coefficient calculating unit 150, and an FBE coefficient calculating unit 160. One main function of the FFE 110 is processing pre-cursor inter-symbol interference signals and a part of post-cursor inter-symbol interference signals in the input signal y(n). One main function of the FBE 130 is processing post-cursor inter-symbol interference signals in the input signal y(n). The decider 120 then generates a decision signal x′(n) according to filtering results of the FFE 110 and the FBE 130.
An FFE coefficient f the FFE 120 needs for operations and an FBE coefficient b the FBE 130 needs for operations are respectively generated by the FFE coefficient calculating unit 150 and the FBE coefficient calculating unit 160. The FFE coefficient calculating unit 150 generates the FFE coefficient f according to a channel impulse response (CIR) estimation vector h generated from the input signal y(n). The FBE coefficient calculating unit 160 generates the FBE coefficient b according to the CIR estimation vector h and the FFE coefficient f.